Effect of stress triaxiality on plastic deformation of metallic glasses

Abstract

Aiming at fabrication of cellular metallic glasses with high mechanical properties, double edge notched samples were designed by orthogonal design method. Compressive tests on those samples were carried out to investigate mechanical responses induced by different notch settings. It was found that the notch tip distance and stress triaxiality are two key factors controlling yield strength and plasticity of notched samples. Besides, free volume theory factoring in hydrostatic stress was incorporated into finite element model to simulate shear band (SB) deformation process for different samples. Combined with experiments, simulations as well as microstructure observations, it was concluded that the notch tip distance effect could be ascribed by transition process between sparsely-intersected and densely-intersected SBs, and the later is the key to plasticity enhancement. Additionally, large stress triaxiality could improve the global plasticity by introducing densely-intersected SBs so as to hinder sample from fracturing along one major SB. The current work could offer useful data in providing direct evidence on fabrication of cellular materials as well as enriching shear band formation mechanism of monolithic metallic glasses.